Forest Vines to Snow Tussocks: The Story of New Zealand Plants
Much further to the east, entirely volcanic and remote from any continent, Tahiti is the highest and largest island of French Polynesia. Geologists believe that Tahiti, as well as other similar islands, rose above the sea in isolation. It would follow that the ancestors of its flora must have arrived by overseas dispersal from already existing islands near and far and directly from continents or indirectly via intervening islands. Possible involvement of a proposed former continent Pacifica was considered in Chapter 1.
Tahiti, along with other very isolated islands, completely lacks certain plant groups. It has no conifers, no species of Nothofagus, no members of the Winteraceae or related primitive families nor of the southern page 231family Proteaceae. Of other important southern families the Myrtaceae is represented by Metrosideros and Decaspermum, the Cunoniaceae by Weinmannia and the Epacridaceae by Styphelia. Near sea level, native vegetation is virtually non-existent, but at higher levels there is a good cover. The forest is low, and in hollows and valleys is dominated by Weinmannia parviflora which, like the New Zealand Weinmannia racemosa, has compound juvenile and simple adult leaves and also often commences life as a low tree fern epiphyte. A long leaved Freycinetia is abundant and there are small orchid and fern epiphytes. Among small trees and shrubs are one large and one small-leaved species of Myrsine, a Meryta and in places a large-leaved Coprosma and the small tree Fuchsia cyrtandroides. In some valleys there are dense tree fern forests which may follow forest clearance as in New Zealand. The tree ferns are species of Cyathea and at least one has the unusual habit of forming more or less spherical bulbils below the leaf crown which drop off to grow into new plants.
On narrow ridge crests species of Metrosideros are conspicuous along with some of the plants from the valleys and in more open places a small-leaved Styphelia. One species each of Ascarina, Macropiper and Ilex are also present. On the ground and sometimes epiphytic is an Astelia and in moist places an Elatostema.
The Tahitian peaks are not high enough for the latitude to support alpine plants.